Hypopigmented mycosis fungoides (MF) is a rare variant of cutaneous T-cell lymphoma. To date, there have been no data published about the efficacy of a twice-weekly regimen of narrowband ultraviolet B (NB-UVB) for the treatment of hypopigmented MF. We retrospectively reviewed 11 patients with hypopigmented MF who were treated with NB-UVB twice weekly between 2001 and 2010. Of the 11 patients, 7 achieved a complete response with a mean of 40 treatments; the remaining 4 patients had a partial response. Upon discontinuation of treatment, three patients had clinical relapse after complete remission. Median time to relapse was 10 months. A twice-weekly regimen of NB-UVB is an effective treatment for hypopigmented MF with minimal side-effects. However, the relapse rate is high, and unfortunately, no clinical or histological features can predict the relapse of the disease.